The invention generally relates to exercise equipment and in particular to exercise treadmills.
Exercise treadmills are widely used for various purposes. Exercise treadmills are, for example, used for performing walking or running aerobic-type exercise while the user remains in a relatively stationary position further, exercise treadmills are used for diagnostic and therapeutic purposes. For all of these purposes, the person on the exercise treadmill normally performs an exercise routine at a relatively steady and continuous level of physical activity. Examples of such treadmills are illustrated in U.S. Pat. Nos. 4,635,928, 4,659,074, 4,664,371, 4,334,676, 4,635,927, 4,643,418, 4,749,181, 4,614,337 and 3,711,812.
Exercise treadmills typically have an endless running surface which is extended between and movable around two substantially parallel pulleys at each end of the treadmill. The running surface may be comprised of a belt of a rubber-like material, or alternatively, the running surface may be comprised of a number of slats positioned substantially parallel to one another attached to one or more bands which are extended around the pulleys. In either case, the belt or band is relatively thin. The belt is normally driven by a motor rotating the front pulley. The speed of the motor is adjustable by the user so that the level of exercise can be adjusted to simulate running or walking as desired.
The belt is typically supported along at least its upper length between the pulleys by one of several well-known designs in order to support the weight of the user For example, rollers may be positioned directly below the belt to support the weight of the user. Another approach is to provide a deck or support surface beneath the belt, such as a wood panel, in order to provide the required support. Here a low-friction sheet or laminate is usually provided on the deck surface to reduce the friction between the deck surface and the belt. Because the belt engages the deck surface, friction between the belt and the deck arises and the belt is therefore subject to wear. Further, most of the decks are rigid resulting in high impact loads as the user""s feet contact the belt and the deck. This is often perceived by users as being uncomfortable and further can result in unnecessary damage to joints as compared to running on a softer surface.
Because the typical treadmill has a very stiff, hard running surface and can become uncomfortable for extended periods or running, some manufacturers have applied a resilient coating to the running surface, such as rubber or carpeting, to reduce foot impact. Unfortunately, these surfaces for the most part have not provided the desired level of comfort because the running surface tends to retain its inherent stiffness. Attempts to solve this problem by using a thicker belt to provide a more shock absorbent running surface have not been successful for the reasons given in U.S. Pat. No. 4,614,337. Specifically, the thickness of the belt has to be limited in order to limit the belt drive power to reasonable levels. In other words, the thicker the belt, the more power that is required to drive the pulley. To keep motor size cost effective, it has been necessary to keep the belt relatively thin. As discussed below, the power of the motor required to drive a pulley is also related to the size of the pulleys.
Pulleys used in current exercise treadmills typically are made of steel or aluminum and as such are relatively expensive to make and are relatively heavy. Therefore, because of tooling, manufacturing and material costs, the diameter of the pulleys are normally no larger than three to four inches.
Additionally, the diameter of the pulley directly affects the power required to rotate the pulley as does the thickness of the belt. If the diameter of the pulleys is relatively small, the thickness of the belt must be kept relatively thin As the diameter of the pulley is increased, the belt may be made thicker for the same amount of power available to drive the pulleys. As discussed above, the thicker the belt, the more shock the belt will absorb.
A further disadvantage of smaller pulleys results from the fact that the reduced surface area of the pulley contacting the belt requires increased tension in the belt in order to transfer torque from the treadmill motor to the belt in some cases, this increased tension can result in decreased belt life.
The pulleys used in current exercise treadmills are typically of a xe2x80x9cconvexxe2x80x9d or of a xe2x80x9ccamberedxe2x80x9d design and as such have a substantially inwardly sloping profile with a portion of the pulley having a larger diameter, or crown, at the center. The convex-type pulley has a rounded crown at its center portion and the cambered-type pulley has a cylindrical center section between conical ends. The purpose of using these two types of pulleys is to maintain xe2x80x9ctrackingxe2x80x9d of the felt because the belt is less likely to slide from side to side on the pulley during rotation if the pulley has a crown. Unfortunately, belts on convex- or camber-type pulleys also tend to be sensitive to improper adjustment and side loading, which can occur when the user is not running on the center of the belt.
Another source of belt wear on existing exercise treadmills results from driving the front belt pulley instead of the rear belt pulley. In a front drive arrangement, the belt has a tendency to develop a slack portion on the upper or running surface of the belt. This tends to increase belt wear. Because existing treadmills have relatively small diameter belt pulleys, it has not been practical to locate the drive motor such that the rear belt pulley can be driven by the motor.
Because most pulleys use the convex- or camber-type configuration as a belt guide, the belts are still sensitive to improper adjustment and side loading. A system whereby a more positive, lateral xe2x80x9ctrackingxe2x80x9d or guidance of the belt is achieved during rotation is therefore desirable.
Many current exercise treadmills also have the ability to provide a variable incline to the treadmill. Normally, the entire apparatus is inclined, not just the running surface. There are a number of exercise treadmills having manual or power driven inclination systems to take advantage of the fact that the exercise effort, or aerobic effect, can be varied greatly with small changes in inclination. For example, a seven percent grade doubles the aerobic or cardiovascular effort compared to level walking or running exercise.
Current inclination or lift mechanisms typically comprise a toothed post in a rack-and-pinion arrangement or a threaded post on which a sprocket attached to the treadmill frame is rotated upwards to lift the treadmill. In both arrangements, the post must be at a height equivalent to the height of travel of the treadmill frame to accommodate the travel of the pinion or sprocket. The length of the post tends to compromise the aesthetics of the treadmill because the post has to extend beyond the plane of the running surface to provide the desired inclination of the running surface. Therefore, a lift mechanism with a large extension rotation which would fit primarily within the treadmill enclosure is desirable.
The treadmill user""s stride also effects the user""s body because the resultant force on the user""s body increases as the stride increases. If the user is running relatively hard, especially over an extended period of time, physical damage to the user""s feet and legs can occur. The larger the resultant force the greater the likelihood of physical damage. If a user""s stride results in a force (measured in pounds) which is about equal to or greater than twice the user""s body weight, the force can be considered excessive. Therefore, a sensor which could measure the force or impact on the treadmill by a user is desirable.
It is therefore an object of the invention to provide an exercise treadmill having a shock absorbent running surface by providing resilient members to support a deck located under a belt.
It is also an object of the invention to provide molded plastic belt pulleys having a large diameter including a drive gear portion integrally molded into one of the pulleys.
It is a further object of the invention to provide an exercise treadmill in which the belt is driven by the rear belt pulley.
It is a further object of the invention to provide a more positive lateral xe2x80x9ctrackingxe2x80x9d or guidance mechanism for the belt.
It is another object to provide a lift mechanism to incline the treadmill running surface that fits primarily within a treadmill enclosure and intermediate the front and rear pulleys.
It is yet another object of the invention to provide a treadmill capable of sensing the impact of the users body on the treadmill and capable of providing that information to the user.
It is still another object of the invention to provide a treadmill in which treadmill belt tension can be reduced without sacrificing reliable operation.
In particular, an exercise treadmill is provided in which a belt is supported for a portion of its length between a pair of pulleys and a deck supported by resilient members in combination with a resilient belt. The thickness of the belt is preferably approximately 0.20 inches. Further, the deck is fixed to resilient members at several points, permitting the deck to partially float on the deck frame when stepped upon, resulting in even lower impact loads on the user feet and legs.
The belt pulley construction can be, alternatively, straight cylindrical, convex, or a cylindrical center section and conical ends (cambered). The belt pulleys also have a relatively large diameter, preferably approximately nine inches. The pulleys are of a molded plastic construction and a drive sprocket portion can be molded as part of the pulley. Possible plastic materials from which the pulleys can be molded include glass-filled polypropylene, polystyrene, polycarbonate, polyurethane and polyester. In some embodiments, bearing seat assemblies can be molded-in to the pulley, when it is originally manufactured, thereby eliminating the need for inserting and fastening bearing seats into molded pulleys.
The use of large diameter pulleys is facilitated through the use of a plastic construction, rather than a steel construction. The large diameter of the pulleys permits the use of thicker belts which can be made to be more shock-absorbing than currently used belts. User comfort is therefore further enhanced. The larger pulleys also reduce the belt tension required for satisfactory belt drive.
A belt position sensor mechanism provides for positive lateral tracking of the belt. As a result, the belt is prevented from laterally sliding too far to one side of the pulley so that it contacts a frame or other portions of the structure, resulting in a reduction of wear or damage to the belt. This arrangement is also less sensitive to improper adjustment and side loading.
The sensor mechanism includes an arm which is spring biased to one edge of the lower surface of the belt, preferably near the front belt pulley. As the belt moves to one side or the other on the front pulley, the arm moves in the same direction as the lateral movement of the belt. In one of two designs, a Hall effect sensor connected to the arm electrically measures the lateral movement of the belt, and the electrical signals are transmitted to a microprocessor. If correction of the belt position is required, the microprocessor will activate a front pulley pivoting mechanism to pivot one end of the front pulley in a longitudinal direction, either towards the front or towards the rear of the treadmill. Because the belt will tend to move towards the lateral (transverse) direction in which the belt tension is lower, the front pulley will be pivoted towards the front of the treadmill to move the belt to the right, and towards the rear of the treadmill to move the belt to the left. The front pulley pivoting mechanism uses a pivot block for holding one end of the pulley axle and a guide block for the other end of the front axle that selectively moves along a longitudinal path from front to rear to create the pivot. In some embodiments, the pivot mechanism drive motor duty cycle is varied as a function of belt position and speed to optimize belt position corrections.
Also, a lift mechanism for the exercise treadmill is provided which includes an internally threaded sprocket assembly which, when driven, forces a non-rotating screw, threaded to the sprocket assembly against the floor thereby inclining the unit. A lift mechanism with a large extension ration which can fit primarily within a side enclosure of the treadmill is therefore made possible. In another embodiment, molded sprockets are driven on the screw by a toothed belt, thereby eliminating the need for chain oiling and providing quieter operation than that produced by a chain drive system.
An impact sensor mechanism is also provided to measure the relative force created on the deck by the treadmill user. The impact sensor mechanism includes an arm, having a pair of magnets, which is spring biased against the lower surface of the deck. As the deck flexes downward when the user""s feet impact the deck, the impact sensor arm is also deflected downward. A Hall effect sensor secured to the frame between the magnets electrically measures the downward deflection of the deck, and the electrical signals are transmitted to a microprocessor. The downward deflection of the deck is a function of the foot impact force and is related to the compressibility of the resilient support members supporting the deck. The microprocessor calculates the impact force by comparing the measured deflection to empirical values. Also, a relative force value is calculated, based on an inputted value for the user""s body weight.
A mold for producing a large diameter pulley having an integral sprocket is also disclosed. In some embodiments, the mold accepts a bearing insert or seat assembly prior to insertion of the plastic pulley material to yield a pulley with a molded-in bearing seat assembly A method for producing these pulleys is also disclosed.